Re: how do I know a subvolume is a snapshot?

[Andrei Borzenkov <arvidjaar@gmail.com>]

17.07.2019 14:19, Nikolay Borisov пишет:
> 
> This is really odd... So this indeed seems to be a userspace problem. 


Of course it is user space problem.

commit 0a0a03554aaf56a6e7245e74fa7d8b3c53f1c20f
Author: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Date:   Fri Mar 23 17:16:49 2018 +0900

    btrfs-progs: mkfs: add uuid and otime to ROOT_ITEM of, FS_TREE

    Currently, the top-level subvolume lacks the UUID. As a result, both
    non-snapshot subvolume and snapshot of top-level subvolume do not have
    Parent UUID and cannot be distinguisued. Therefore "fi show" of
    top-level lists all the subvolumes which lacks the UUID in
    "Snapshot(s)" filed.  Also, it lacks the otime information.

    Fix this by adding the UUID and otime at the mkfs time.  As a
    consequence, snapshots of top-level subvolume now have a Parent UUID and
    UUID tree will create an entry for top-level subvolume at mount time.
    This should not cause the problem for current kernel, but user program
    which relies on the empty Parent UUID may be affected by this change.


What about the question - is there tool to fix existing filesystem by
adding this information?